Dear Eileen,

The damage on your Illawarra Flame tree could either be caterpillar or possum damage. Being such a large tree, it would be difficult to spray, however Yates has a wonderful new product available - Yates Possum Repellent Spray helps protect your precious plants by deterring possums from browsing on sprayed plants.
Features
Contains a special combination of ingredients that help reduce possums browsing on plants.
Lasts for up to 7 days or more with regular re-treatment.
Can be used on ornamental and edible plants and has only a 1 day withholding period.
The formulation was developed by Professor Lynne Selwood and is protected by a patent granted to the University of Melbourne.

A healthy tree will produce new leaves as it grows so I would suggest you keep it healthy with regular fertilising and adequate watering during the warm months. If you prefer to use a pesticide for the caterpillar damage, I would suggest Yates Success Ultra to control this pest. Good luck